1. Field of the Invention
The invention relates to an optical disc recording/reproducing apparatus, and more particularly to a method for distinguishing a unbalanced disc of the optical disc recording/reproducing apparatus.
2. Description of the Prior Art
By the advancement of the manufacturing ability of the optical disc drive, the recording/reproducing speed increases continuously. High recording/reproducing speed needs the rotating motor having high rotating speed, and at this time, the quality of the optical disc will influence much to the recording/reproducing efficiency. The unbalanced disc is produced by the error during manufacturing. This makes the mass central of the unbalanced disc is not at the center of the disc. When the unbalanced disc rotates at high speed, it will vibrate and produce unpleasing vibration noises, and this may accelerate the mechanical wear of the optical disc drive. More importantly, this may induce the optical disc being scraped or abraded by the optical pickup head. Therefore, it is an important subject to well control the vibration due to the unbalanced disc.
Generally speaking, when the unbalanced degree of the optical disc is too large, the optical disc drive would lower down the rotating speed to decrease the vibration due to the unbalanced disc, which means sacrificing the reproducing speed to ensure the safety and the stability during reproducing process. However, the qualities of disc on the market are irregular, and the unbalanced degrees of defective discs also have differences. If substantially decreasing the rotating speed of the unbalanced disc to prevent vibrations, the reproducing speed of the optical disc drive will be greatly influenced, and this also reduces the marketing competitiveness of the optical disc drive. Hence, accurately distinguishing the unbalanced degree of the unbalanced disc and automatically adjusting the rotating speed of the optical disc drive according to the unbalanced degree become the key point to increase the average reproducing speed.
Commonly speaking, the unbalanced degree of the optical disc influences the reproducing speed of the optical disc drive. The recent method for distinguishing the unbalanced degree of the optical disc is affected by the orientation of the optical disc drive or the scratches on the optical disc.
U.S. Pat. No. 6,934,232B2 and 6,965,548B2 are calculating the amounts of focus error (FE) signals and the amount of track error (TE) signals respectively in a cycle for distinguishing the degree of the unbalanced disc. In US Patent Application Publication No. 2004/0013066A1, it compares the voltage value of the push-pull (PP) signal with the predetermined threshold voltage value. When the voltage value of the PP signal is larger than the threshold voltage value, the optical disc is determined to be an unbalanced disc. However, those signals mentioned above may be influenced by noises produced by the orientation of the optical disc drive, for example horizontal orientation or vertical orientation, and the scratch or other defects on the optical disc, which will affect the accuracy of the distinguished results. Therefore, the present invention provides a method for lowering the disturbances of noises and accurately distinguishing the degree of the unbalanced disc.